1. Field of the Invention
The present invention relates to quantum wires formed on a substrate, a manufacturing method thereof, and a device having quantum wires on a substrate.
2. Description of the Related Art
By virtue of its nanometer-size effect, the quantum wire can provide novel physical properties that are different from bulk properties. For example, as shown in FIG. 1, in the silicon (Si) quantum wire, the band gap increases as the wire diameter decreases. Further, a material having an indirect transition band gap in a bulk state is changed to a material having a direct transition band gap. As a result, in the silicon quantum wire, the efficiency of light emission due to excited electron-hole recombination is increased remarkably and the emission wavelength is shifted to the shorter wavelength side, which enables visible light emission.
The silicon quantum wire which can provide the above physical properties is conventionally manufactured by etching a silicon substrate by electron beam lithography or some other method. However, it is difficult for this method to manufacture, in an integrated manner, silicon quantum wires having an equal shape over a wide area.
In view of the above, it has been proposed to growing a number of silicon quantum wires directly on a silicon substrate by using a VLS (vapor-liquid-solid) method (refer to E. I. Givargizov, J. Vac. Sci. Techno. B11(2), pp. 449). In this method, after melted alloy droplets of silicon and gold are formed on the surface of a silicon substrate by evaporating gold (Au) on the silicon substrate, silicon quantum wires are grown by heating the substrate while supplying a material gas of silicon (refer to Wagner et al., Appl. Phys. Lett. 4, No. 5, pp. 89, 1964, and Givargizov, J. Cryst. Growth, 31, pp. 20, 1975).